The present invention relates to a structure of an optical transmission channel for use in a fiberscope, an optical fiber sensor and the like, having an illuminating light transmission channel, an information light transmission channel and various kinds of auxiliary transmission channels.
The conventional optical transmission channel for use in a fiberscope for making observations in a heart and blood vessels, as disclosed in Japanese Laid-Open Patent No. 55-151936 (1980) titled "Internal Observation Apparatus", requires special features because the heart and blood vessels are filled with an opaque liquid i.e. blood.
Referring now to FIG. 1, a flexible cable portion 4 of a fiberscope encloses illuminating light transmission fibers and an information light transmission image fiber (image direct-transmission fiber optics, and a transparent balloon 3 is provided at a pointed head thereof in order to observe the internal wall 1 of a heart.
The balloon 3 is flexible and can when bulged displace blood 2, which obstructs the field of vision in front of the fiberscope thereby permitting observation of the internal wall 1 of a heart.
Reference numeral 6 designates an image-receiving adaptor for observing transmitted images, reference numeral 8 designates a light source of an illuminating light, and reference numeral 9 designates a syringe for expanding and contracting said balloon 3.
In prior fiberscopes the flexible cable portion 4 as shown in section in FIG. 2, has four illuminating light transmission plastic fibers 11 arranged around an image fiber 10 and a tube 12 for expanding and contracting said balloon 3, housed in said flexible cable portion 4.
However, an optical transmission channel according to the above described conventional art has the following disadvantages:
(1) Large gaps are formed among said image fiber 10, said plastic fibers 11 and said tube 2 and thus the cross-sectional area of said flexible cable portion 4 is inefficiently utilized since said image fiber 10, said plastic fibers 11, said tube 12 have circular cross sections and they are housed in said flexible cable portion 4 also having a circular cross section.
(2) The labor costs for collecting and branching of the fibers and tube are high.